Some of systems including various instruments (e.g., measuring instruments) are configured to monitor operation statuses of the respective instruments and draw attention of a user by informing alarms to the user when abnormality occurs, etc. Recently, alarm display devices which visually or aurally inform alarms to users from various monitoring systems and various instruments are provided.
WO2013/132999A1 discloses an alarm display device. The alarm display device of WO2013/132999A1 includes a display unit, an alarm information acquiring module, an information memory, a transmission source classification list memory, an importance list memory, a display target specifying module, an information selecting module, an alarm information displaying module, and a sound notifier which informs issuance of an alarm by sound. The alarm information displaying module only displays display alarm information in the form of a list. The display alarm information is selected, by the information selecting module, from display targets specified by the display target specifying module, based on lists stored in the memories. Thus, according to WO2013/132999A1, by only displaying the alarm information specified as the display target in the form of a list, the alarm information can be displayed in a visibly easily understandable manner.
JP2003-322693A discloses a monitoring control system having a time synchronization method. The monitoring control system of JP2003-322693A includes a monitoring device, control devices, a reference clock, and an internal clock. The internal clock has a clock function to calculate an internal time by combining a time signal with a supplemental time, and synchronizes, by the clock function, the internal time with a reference time of the reference clock by one millisecond unit. The time signal is synchronized with the reference time. The supplemental time is obtained by counting a clock signal having one millisecond cycle. Thus, according to JP2003-322693A, in the system including two or more control devices which store a change of a state of a monitoring target along with the time of the change, the time can be synchronized among the control devices highly accurately.
In WO2013/132999A1, the alarm information is mainly displayed on a display screen. Note that, although the alarm display device of WO2013/132999A1 includes the sound notifier, the sound notifier aurally informs the alarm to the user simply at the timing of the alarm issuance. However, for example, on a ship where various kinds of navigation instruments are equipped, when alarms are issued in a plurality of instruments and alarm sounds are outputted therefrom, it is difficult to distinguish the kinds of the alarm sounds and the output sources, and there is a possibility of causing uncomfortableness to the user due to noises caused by the plurality of alarm sounds outputted here and there.
Moreover, although JP2003-322693A discloses the configuration of the monitoring control system which synchronizes time among the plurality of instruments, it does not disclose anything about outputting an alarm sound or controlling a timing of the output.